Ubuntu20.04 VM network doesn't seem to be working with SR-IOV enabled VSwitch

Shubham Chaudhary 1 Reputation point
2022-08-31T23:47:55.517+00:00

We are running Ubuntu-20.04 guest on Windows server 2022 Hper-V with SR-IOV enabled. On the Network status of the ubuntu 20.04 guest we see - OK(SR-IOV active). but inside VM there's no network connectivity, and we can't seem to ping gateway etc.

Via dmesg we see that VF is active and is assigned to the VM. (log: hv_netsvc eth0: Data path switched to VF: enp40752s1.)

Tried disabling Virtual Machine Queue on VM network adapter settings, but that didn't seem to work either.

Host network adapter is Broadcom NX-E 10g Base-T. Ubuntu 20.04 guest Kernel version: 5.15.0.1017-azure ( linux-azure tools installed )

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  1. Limitless Technology 39,351 Reputation points
    2022-09-02T07:45:42.26+00:00

    Hello there,

    Disable the firewall, and then test the result. If the problem is resolved, verify the firewall settings, and then re-enable the firewall.

    Use Network Watcher IP Flow Verify and NSG Flow Logging to determine whether there is a Network Security Group (NSG) or User-Defined Route (UDR) that is interfering with traffic flow.

    Try some additional Troubleshooting from this link https://learn.microsoft.com/en-us/azure/virtual-network/virtual-network-troubleshoot-connectivity-problem-between-vms

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  2. risolis 8,701 Reputation points
    2022-09-03T01:30:55.71+00:00

    Hello @Shubham Chaudhary

    Thank you for your heads up.

    I can not deny that this brought my attention so, I started looking for the accurate step to solve this and I found the next information as shown down below: 

     ifconfig displays “RUNNING” flag when the cable is not connected.  
This is a known issue in the Linux operating system stack.  
Workaround  
Use “ip link show” to display the “Oper status” value.  
2. In certain SKEWs of controllers, PING is not working when attempting to bridge the  
1G or 10G ports to the virtual machines when SR-IOV is enabled for 10G ports in the  
BIOS.  
This issue occurs due to limitations of the virtual Ethernet bridge. All transmitted  
broadcast packets are looped back by the controller. This affects the functionality of the  
Linux bridge, as it appears as if the same ARP broadcast packets are received on two  
different interfaces.  
Driver for Linux Release Notes 10  
P011044-01A Rev. A  
Workaround  
a) Set the aging of the bridge to 0 using the following command:  
“brctl setageing <bridge> 0”  
This causes the bridge to behave like a hub and flood the packet to all the ports  
(except the one on which the packet arrived) every time. This may impact  
performance. If you have only two interfaces on this bridge (one NIC interface and  
virbr0-nic), there is no performance impact.  
b) Another option may be to use the MacVTap interface to the guest instead of the  
bridge interface.

    For further info about that please direct yourself to this link >>> https://docs.broadcom.com/doc/12356080

    I hope this can be a great help to address this concern soon : )

    Have a good one!

    Cheers,

    Please "Accept the answer" if the information helped you. This will help us and others in the community as well.